Bellows type expansion joint for tubular conduits



Jan. 18, 1955 J PJZALLEA 2,699,959

BELLOWS TYPE EXPANSION JOINT FOR TUBULAR CONDUITS Original Filed Dec.10, 1948 3 Sheets-Sheet l f I J) NVENTOR JAMES F? ZALLEA ATTORNEY Jan.18, 1955 J. P. ZALLEA 2,699,959

BELLOWS TYPE EXPANSION JOINT FOR TUBULAR CONDUITS Original Filed Dec.10, 1948 5 Sheets-Sheet 2 INVENTOR James R ZALLEA BY I ATTORNEY J. P.ZALLEA BELLOWS TYPE EXPANSION JOINT FOR TUBULAR CONDUITS Jan. 18, 1955 3Sheets-Sheet I5 Original Filed Dec. 10, 1948 Ihwentor QHMES F- ZALLEA(morneg BELLOWS TYPE EXPANSION JOINT FOR TUBULAR CONDUITS James P.Zallea, Wilmington, Del.

Original application December 10, 1948, Serial No. 64,488. Divided andthis application December 7, 1950, Serial No. 199,600

Claims. (Cl. 28590) This invention relates generally to expansion jointsand more particularly to expansion joints having as a part thereofone-piece toroidal-shaped bellows elements and to the method of makingthe same, this application being a division of application Serial No.64,488, filed December 10, 1948, now Patent No. 2,631,648.

It is a principal object of the present invention to provide expansionjoints having thin-walled bellows elements which are capable ofwithstanding very high internal pressures, which are usuable with theheavy gauge pipe necessary in a pipe line for such pressures and whichpermits a maximum of flexings before any failure due to materialfatigue.

Also among the principal objects of the present invention is to providea one-piece thin-walled hydraulically bulged bellows element capable ofwithstanding high internal pressures and a maximum number of flexingsbefore failure due to material fatigue.

It is a further object of the present invention to providetoroidal-shaped bellows elements of one-piece con-- struction whichpermits uniform flexing throughout the area of the bellows and which hasno points of stress concentrations which would reduce the number offlexings before failure of the bellows due to material fatigue.

it is also an object of the invention to provide expansion joints withone or more one-piece hydraulically bulged toroidal-shaped bellowselements having integral tubular sections extending axially fromopposite sides thereof, as well as to provide a simple and effectivemethod of forming such bellows by hydraulic bulging of a tubular memberwithout the use of any restraining dies.

With the above objects in view, the invention further resides in thecombination and arrangements of parts and in the details of constructionherein described and claimed; it being understood that the specificembodiments of the invention described herein are illustrative and thatmodifications thereof falling within the scope of the appended claimswill be apparent to persons skilled in the art.

In the drawings:

Figure 1 is a sectional view of a portion of a conventional hydraulicpress showing in full lines the upper and lower platens with acylindrical bellows blank positioned therebetween, and in dotted linesan intermediate posi-' tion of the platens and a partiallyformed-bellows;

Figure 2 is a view similar to Figure l'showing the lower platen inraised position with the toroidabshaped bellows fully formed;

Figure 3 is a view similar to Figurc'l but showing a modified form ofcylindrical bellows blank, the dotted lines showing the lower platen inraised position with the bellows fully fonned;

Figure 4 is a sectional view of a bellows element formed 7 in accordancewith the present invention with pipe nipples encircling the integrallyformed tubular sections of the bellows;

Figure 5 is a sectional view of a bellows element showing its integraloppositely extending tubular sections turned over flanges of anexpansion joint adapted to be bolted to a pipe line or other equipment;I

Figure 6 is a sectional view of a plurality of bellows elements weldedto pipe nipples to form an expansion joint having a plurality ofbellows;

Figure 7 is a sectional view of anothermodified form of cylindricalbellows blank having an encircling band midway thereof;

Figure 8 is a sectional view of a p'airof integral tor- States Patent 0ice oidal-shaped bellows as made from the blank shown in Figure 7.

Heretofore toroidal-shaped bellows elements for expansion joints havebeen formed from a pair of like hollow hemitoroidal-shaped blanks havingtheir outer circumferential edges butt-welded together. The innercircumferential edges of these butt-welded blanks, axially spaced fromeach other, were usually secured to axially extending pipe sections byedge or fillet welding. The prior art bellows unit so produced thuscomprised four separate members which when welded together to form acomposite unit, was subject to certain decided disadvantage inherent inthe welded construction.

Inasmuch as it was necessary for successful butt-welding of the outercircumferential edges of the hemitoroid members of the bellows that thewall thickness or gauge of the metal used be not less than a prescribedminimum, such prior construction of the bellows element necessarilyinvolved the use of metal of such thickness as reduced the flexibilityof the bellows and its flexing capability to less than that of a bellowsmade of thin gauge material. Furthermore, because there is a limit tothe gauge ratio between the metals respectively forming the hemitoroidsand the pipe sections for successful welding together of these metals,when the pipe sections were of relatively heavy gauge, as when they wereof large diameter or designed for use under high internal fluidpressure, the metal of which the hemitoroid members were formed werenecessarily of relatively heavy gauge, thus limiting the flexingcapability of the bellows element. Also, the weldlines between thehemitoroid members and the pipe sections, being directly in the regionsof flex, produced points of stress concentration resulting in reducedflexing capability of the bellows and premature destruction thereof.

In the present invention these disadvantages are overcome by theprovision of a hydraulically bulged one-piece toroidal-shaped bellowselement having integrally formed oppositely extending tubular pipesections. By reason of the hydraulic bulging process of the presentinvention, not only may a bellows element be formed of the minimum gaugeor wall thickness necessary to withstand a designated internal pressure,but also it insures that the toroidal-shaped portion of the element willbe subject to uniform flexing throughout and will be capable of amaximum number of flexings before failure due to material fatigue. Dueto the absence of any lines of weld within the one-piece toroidal-shapedportion of the bellows element there are no points of stressconcentrations therein, thereby permitting uniform flexing throughoutthe bellows with no zones or areas of maximum or minimum flexing stress.

It is well known that for a given metal the thinner its gauge thegreater the number of flexings is it capable of withstanding beforematerial failure. By the process of the present invention, the bellowselement may be formed of the minimum wall thickness required for a giveninternal pressure thereof to thereby increase its flexing capability andconsequently its useful life.

For purposes of illustrating the principles underlying the presentinvention, the following practical examples may be given. Assuming theneed for a corrugated expansion joint or bellows unit in a 30 inchdiameter pipe line designed to withstand an internal pressure of 1000pounds per square inch, the pipe line being formed of carbon steel anddesigned for a working stress of 11,000 pounds per square inch, the wallthickness of the pipe would be 1.36 inches according to the formulawherein Tp is the pipe wall thickness, P is the working pressure, Rp isthe pipe line radius and S is the permissible working strength of thecarbon steel pipe. Employing in conjunction with such pipe line astainless steel toroidal bellows having a circular section of 2 /2 inchdiameter, the theoretical minimum wall thickness or gauge thereof shouldbe 0.05 inch, according to the same formula wherein Tt, is the toroidwall thickness, P is the working pressure, Rt, is the radius of thetoroid circular section and S is the permissible working strength of thestainless steel toroid, i. e., 25,000 pounds per square inch.

For an internal working pressure of only 500 pounds per square inch inan expansion joint pipe line of the above specified diameters of pipeline and toroidal bellows, the wall thickness or gauge of the pipe linewould be 10.681 inch, while that of the toroid would be 0.025 11101.

In either case, the gauge of the metal forming the toroid is too lightfor practicable butt welding together of two or more parts formedthereof, and it is because of this that welded toroidal elements haveheretofore ben formed of a gauge much heavier than that actuallyrequired to withstand a given internal operating pressure. The hydraulicbulging process of the present invention makes possible utilization of awall thickness for the toroid which closely approaches the theoreticalminimum for the metal of which it is formed when employed for aparticular pipe line working pressure, at the same time that it permitsformation of a toroidal bellows element having a materially increasedworking life, it being noted in this latter respect that when the toroidwall thickness is reduced one-half its life expectancy is increasedapproximately eight times.

In the hydraulic bulging method of forming the toroidalshaped bellows,the cylindrical blank from which it is made is deformed from withinwithout the use of any external restraining dies and as the oppositeaxially extending tubular sections are integral with the toroidshapedportion of the bellows, they may be joined to suitable pipe nipples,spacer or supporting elements by suitable welds which are not in an areaof flex and, therefore, not restrictive of the flexing life of thebellows. These tubular sections may be secured to embracing pipeelements by resistance seam welding, brazing or even soldering, therebypermitting practically any thickness of bellows metal to be welded toany thickness of pipe.

The present invention will be best understood by referring to thedrawings, wherein Figures 1 and 2 show part of a conventional hydraulicpress having upper and lower platens 11 and 12, either of which may bemovable relatively to the other, with a cylindrical shell or blank 13therebetween from which the one-piece toroidalshaped bellows element ismade by hydraulic bulging on the press. A threaded nipple 14 having anut 15 threaded thereon is adjustably supported in opening 16 of upperplaten 11, the nut 15 being wider than opening 16. The nipple 14, withits vent conduit 17 suitably secured to its upper end, supports at itslower end a flat annular member 18 just below the platen 11 and insidethe upper end of blank 13. An annular member 13, positioned with itsupper face parallel to the lower face of platen 11, is threadedlysecured to and supported by the lower end of nipple 1 5. Thus, thehydraulic pressure fluid, e. g., water, may flow from the interior ofblank 13 to and through the vent conduit 17.

The annular member 18 of outside diameter slightly less than theinternal diameter of blank 13 is circumferentially undercut on its upperface to provide an annular ledge or seat 19, the walls of which meetpreferably at substantially right angles. Fitting snugly on the annularseat or ledge i? in contact with the undersurface of platen 11 and theinside surface of that portion of blank 13 extend ing between the ledge19 and platen 11 is a compressible sealing ring 20, of rubber or thelike, which is adapted, when hydraulic pressure is exerted upon annularmember 18, to be compressed to form a water-tight seal between theparts. It will be understood that the sealing ring 20, placed uponmember 18 before the latter, is threaded upon nipple 14, may beinitially compressed after blank 1.3 is in place by manually orotherwise turning adjustable nut 15, whereupon further compression byhydraulic action on member 18 will form a water-tight seal at the upperconfined end of the tubular blank.

A similarly shaped fiat annular member 21 with an annular seat or ledge22 is fitted with a compressible sealing ring 23 in Contact with theinside surface of the lower end of blank 13 and with the upper surfaceof lower ,laten 12, so that when hydraulic pressure is exerted upon theupper surface of member 21, the sealing ring 23 may be compressed toform a water-tight seal between the parts. Annular member 21, spacedfrom platen 12 to allow for movement thereof in compressing the sealingring 23, is

also fitted with a conduit nipple 24, the latter being extended freelythrough a suitable opening 25 provided in the platen 12 and beingconnected to a conduit 26 for supplying fluid (e. g. water) underpressure into the interior of the tubular blank 13. As in the case ofthe upper nipple 14, the nipple 24 is also provided with a nut 15 forpreliminarily drawing the member 21 toward its platen 12 to compress thesealing ring 23 sufficiently to seal the lower end of the tubular blank13. In accordance with conventional practice the conduit 26 may beprovided with suitable valve means (not shown) for exhausting the fluidfrom the interior of the blank upon completion of the bulging operationof the present invention.

in order to form the toroidal-shaped portion of the bellows element byhydraulic bulging alone, dies in the form of encircling rings 27 and 28are provided adjacent upper and lower portions of blank 13, thoseportions of the blank inside the rings forming the oppositely extendingaxially aligned tubular sections 29 and 34) (Figure 2) of the completed.bellows element, while the portion of the blank between the rings formsthe toroid-shaped portion 31 (Figure 2) thereof. It will be obvious thatthe size of the toroid 31 to be formed will depend upon the length ofblank 13 extending between the ring dies 27 and 28.

it will be understood that ring dies 27 and 28 of such predeterminedlength may be employed as will insure that the completed toroid 31 willbe spaced freely between the platen-supported members 34 and 35. Thering dies 27 and 28, with their free edges rounded, as at 32 and 33, maybe formed as integral extensions of members 34 and 35 which arerespectively mounted upon the upper and lower platens 11. and 12.Preferably, the upper member 34 is secured to the upper platen 11 inencircling relation with respect to tubular blank 13 by bolts 36 inthreaded engagement with the marginal edge of the platen, while in thecase of the lower member 35 its own weight is sufiicient to hold it inposition upon the lower platen 12 in encircling relation with respect tothe tubular blank 13. However, if desired, the lower member 355 may alsobe bolted to its associated platen 12, in the same manner that themember 34 is bolted to the upper platen 11.

Suitably provided in the till and drain connection 26 is a three-wayvalve (not shown) by means of which water under suitable pressure may bedelivered into the interior of the tubular blank 13 when the bulgingoperation is commenced, or discharged therefrom when the bulgingoperation is completed. The vent connection 1'? may be suitably providedwith a closure valve (not shown) by means of which the blank 13 may beair-vented and by means of which'a certain amount of water may beremoved from within blank 13 from time to time as the platens 11 and 12move toward each other and so compensate for the resulting reduction inthe space therebetween during the bulging operation.

In the operation of the hydraulic press 1% with the blank '13 and ringdies 27 and 28 initially in the positions shown in full lines in Figure1 and with the closure valve of vent 17 opened, a suflicient volume ofwater to fill blank 13 is delivered into the interior thereof by way ofthe passages 24 and 25 in communication with the main supply conduit 26,whereupon the valve in vent 17 is closed and pressure begins to beexerted upon the enclosed water from the pressure supply 2d. Withopposite circumferential edges of blank 13 in contact with platens 11and 12, hydraulic pressure upon the flat annular members 18 and 21 willcause them to move slightly in opposite directions toward said platens,thereby compressing the sealing rings 20 and 23 to form a water-tightseal at each end of the blank 13. When the interior of the tubular blank13 is thus subjected to hydraulic pressure, the movable platen, whichmay be either 11 or 12 but which is here shown as 12, is simultaneouslyraised toward the fixed platen, here shown as 11, and when the pressureexceeds the yield point of the metal of blank 13, the latter bulgesoutwardly centrally thereof into its uniformly curved (i. e., circular)form as shown in dotted lines in Figure 1.

It will be noted that the bulging operation is confined between the ringdies 27 and 28, the reversely curved portions'37 and 38of the toroidwhich are formed as an incident to the bulging operation being shapedabout the rounded free edges-of the ring dies. The operator of the presscontinues to raise platen 12, apply pressure from connection 26, orremove water from within blank 13 by vent .17,":as'required, to continuethe bulging process upon blank 13 until the center thereof has reachedits desired outermost diameter. At this point, as shown in Figure 1, thecurved section of blank 13 has not assumed its final circular form, thislatter form of the bulged portion of the blank being obtained only afterthe relatively movable platens of the press assume their final positionsas shown in Figure 2. It will be noted that as the metal of blank 13 isbulged outwardly it becomes progressively and uniformly thinner from amaximum thickness at the tubular sections 29 and 30 to a minimumthickness at the point of maximum diameter of the toroid section 31,this thinning being accompanied, however, by a compensating increase inthe strength of the metal due to the cold working thereof. Because thehydraulic bulging process applies fluid pressure uniformly against theinternal surface of the unconfined portion of the tubular blank 13, suchportion is subject to substantially uniform deformation to provide atoroidal section having uniform strength throughout.

The present invention, by the process described, provides a one-piecetoroidal-shaped bellows element T with integral oppositely extendingaxially aligned tubular sections 29 and 30, the toroidal-shaped portion31 thereof being formed entirely by hydraulic bulging without the use ofany restraining dies and being connected to each tubular section by thereversely curved portions 37 and 38 formed over ring dies 27 and 28. Theentire flexing portion 31 of the bellows element is concave to pres surewhile the reversely extending portions 37 and 38, which will beadequately supported in the expansion joint by members of the same shapeas ring dies 27 and 28, are convex to pressure.

For securing the bellows element T, formed as above described, in a pipeline, its tubular sections 29 and 30 are respectively provided withoppositely extending tubular members, such as the pipe nipples 39 and 40shown in Figure 4. These pipe nipples 39 and 40 are respectivelyprovided with rounded circumferential edges 41 and 42 which more or lesssnugly nest in the reversely curved portions 37 and 38 of each bellowselement T, the nipples being secured to the tubular sections 29 and 30by any convenient form of welding or brazing. In the case of extremelythin metal resistance seam welding is preferably employed, while withthicker metal the tubular sections 29 and 30 may be joined to pipenipples 39 and 40 by lap welding, shown at 4343 interiorly of thenipples. The outer free ends of the pipe nipples 39 and 40 are adaptedto be welded or otherwies secured directly into a pipe line.

In one form of expansion joint, as shown in Figure 5, the supportingnipples for the bellows element are adapted to be bolted into the pipeline and to this end such nipples each include an axially extendingmember 44 having its outer free end welded, as at 45, to a boltingflange 47, the latter being suitably provided with bolt holes 48. Thebolting flanges 47-47 encircle the extra long tubular sections 4949 ofbellows element T, the tubular sections extending beyond the flanges andbeing turned over the outer faces thereof to provide what is known as aVanstoned construction. The rounded circumferential free edges 50 and 51of pipe sections 4444 snugly nest into the reversely curved portions 37and 39 of the bellows element T, as in the previously described form ofthe bellows unit.

Figure 6 illustrates still another form of bellows unit constructed inaccordance with the present invention. In this form of construction, aplurality of the bellows elements T are connected together in axiallyaligned relation by a series of interconnecting tubular sleeves 52, eachof which is of a length at least equal to the combined lengths of a pairof the adjoining tubular extensions 2930 of the bellows element. As inthe case of the pipe nipples 3940, in each of the connecting sleeves 52the opposite ends thereof are rounded, as at 53 and 54, to snugly fitinto the reversely curved portions 37-38 of the bellows elements. Anyconvenient or required number of axially aligned elements T may bejoined together in this manner to form a multiple-bellows unit expansionjoint. As illustrated in Figure 6, the multiple-bellows unit comprisesfour toroidal-shaped bellows elements T joined together by threeconnector sleeves 52, the oppositely extending tubular end sections 29and 30 of the end elements having pipe nipples 39 and 40 securedthereto. In this embodiment, it is preferred that the tubular sections29 and 30 of the bellows elements be secured to the sleeves 52 and tonipples 39 and 40 by resistance welding, each line 55 of which is formedof a series of overlapped spot welds to provide a fluid tight jointbetween the welded elements.

The expansion joint shown in Figure 4 as having been made by weldingencircling pipe nipples 39 and 40 to the tubular sections 29 and 30 of apre-formed toroidalshaped bellows element may be constructed in anotherway. As illustrated in Figure 3, a blank 13 of cylindrical form withencircling pipe nipples 39 and 40'welded, as at 7070, to opposite endsthereof may be positioned in the hydraulic press 10 between its platens11 and 12 in a manner similar to that shown and described in Figure l.Inasmuch as the blank from which the expansion joint of Figure 4 is tobe formed comprises the cylindrical shell 13 and the nipples 39 and 40welded to the ends thereof, the latter may be employed in themselves asthe forming dies about which the bulging of the shell takes place. Thus,except for the fact that the nipples 39 and 40 replace the ring dies 27and 28, the operation illustrated in Figure 3 is similar to that ofFigure l, the hydraulic press being modified only in that the annularmembers 57 and 58 thereof as employed in Figure 3 are centrallyapertured to diameters suflicient to embrace the nipples 39 and 40.

It is within the scope of the present invention to provide a one-piecebellows element S having a pair of axially spaced toroidal sections 31-31 as shown in Figure 8, such element being formed from a blankingmember 59 as shown in Figure 7 by the hydraulic bulging process of thepresent invention. The blanking member 59 is similar to shell blank 13,except that it is longer and is provided .with a centrally locatedencircling member 60 suitably welded thereto. This member 59 ispositioned in the hydraulic press 10 in exactly the same manner as blank13 with the exception that platens 11 and 12 are spaced the requireddistance apart to receive the longer blank. The embracing sleeve member60 may be secured to the tubular shell 59 in any suitable manner, as byspot welds 61 or it may be free from the shell, in which case the sleeve60 is supported centrally of blank shell 59 by any suitable externalmeans until initial bulging of shell 59 above and below the sleevemember 60 operates to hold the same in place. In the present instance,guide die rings 27 and 28 and opposite rounded circumferential edges ofthe sleeve 60 are the means about which the axially alignedtoroid-shaped portions 31 31 are bulged in the hydraulic press 10, thereversely extending curved section 37* -38 being formed by the roundededges of the ring dies 27 and 28. The double toroidshaped portions fl-31 of bellows element S are joined together by the intermediate tubularsection 62 of the blank 59 embraced by the sleeve member 60 the oppositeends of which fit into the reversely curved sections 63--63 I of theshell, the latter sections being respectively formed by the oppositerounded ends 64-64 of the sleeve 60. Tubular sections 29 and 30 axiallyaligned with each other and with tubular section 62 are integrallyformed with the toroid-shaped sections 31*-31 and extend in oppositedirections from the outer sides of each, being respectively joinedthereto by the outer reverse curved sections 37 and 38 In order tosupport the double toroid element S for use in a pipe line, pipe nipplessimilar to those designated by the reference numerals 39 and 40 inFigure 4 may be secured to the tubular end sections 29 and 30 of thebellows by welding, brazing or the like.

It will be apparent that by securing a plurality of sleeve members 60 tothe member 59 in suitably spaced relation, a one-piece bellows elementhaving a plurality of axially spaced toroidal elements may be formed ina single hydraulic bulging operation, the number of such toroidalelements exceeding by one the number of intermediate sleeve members 60preliminarily secured to the tube 59. Thus, instead of forming a bellowselement with only two toroidal elements as in Figure 8, a bellowselement may be formed with three or any greater number of such toroidalelements.

It will be understood, of course, that the present invention issusceptible of various changes and modifications which may be made fromtime to time without departing from the general principles or realspirit thereof, and it is accordingly intended to claim the samebroadly, als well as specifically, as indicated by the appended 0 arms.

Whatv is claimed as new and useful is:

1. In an expansion jointfor a pipe line or the like, a unitary bellowselement: of hollow toroidal shape formed of a tubular blank to havepermanently formed an annular central wall part of generally circularshape in transverse section which is concave to any internal pressure towhich the joint may be subjected, said annular central wall part beingtransversely curved through an arc substantially greater than 180degrees and terminating at opposite sides thereof in a pair of axiallyspaced annular side wall parts which define therebetween a relativelynarrow opening extending circumferentially about the annular base ofsaid central wall part, said side wall parts being each similarlycurvedreversely throughout with respect to the curvature of said.central part and thus convex to said internal pressure, the reverselycurved side wallparts providing respectively on opposite sides of thecentral wall part of the bellows element a pair of oppositely presentingannular indentations equally spaced radially from re centrallongitudinal axis of the bellows element, the said indentations beingeach of a same radius substantially less than that of the central wallpart, the opposite sides of said annular central wall part of thebellows element and said reversely curved side wall parts thereof beingsymmetrically disposed with reference to the median plane of the elementextending normal to the axis thereof, said reversely curved side wallparts being respectively provided with axially alined tubularextremities of equal diameter at opposite sides of said main centralwall part, means snugly fitted in the indentations formed by saidreversely curved side wall parts of said bellows element and extendingaxially from opposite sides thereof in embracing relation to saidtubular extremities for reinforcing and supporting said side wall partsagainst deformation under the influence of said internal pressure, whilepermitting said central part to flex freely upon expansion andcontraction of said joint, and means for securing said reinforcing andsupporting means respectively to said tubular extensions, said securingmeans being spaced axially from said reversely curved side wall parts,said bellows element being further characterized in that thetransversely curved central wall part and the reversely curved side wallparts thereof are formed of continuously homogeneous metal entirely freeof any circumferentially extending welds.

2. In an expansion joint for a pipe line or the like, a bellows elementas defined in claim 1 wherein said means for supporting said reverselycurved side wall parts against deformation under the influence of saidinternal pressure comprise oppositely extending tubular members securedto said bellows element in mial extension thereof, the ends of saidtubular members respectively adjoining opposite sides of said bellowselement being rounded to a shape which is complemental to the transversecurvature of said annular indentations and being snugly nested in saidindentations.

3. in an expansion joint as defined in claim 1 wherein the means forsecuring the reinforcing and supporting means to the tubular extensionsof the bellows element are welds disposed along lines extendingcircumferentially about said tubular extensions, all of said welds beingspaced axially from said reversely curved side wall parts of the bellowselement.

4. In an expansion joint for a pipe line or the like, a a plurality ofhollow toroid-shaped unitary bellows elements formed of tubular stock sothat each of said elements has permanently formed an annular centralwall part of generally circular form which extends in transverse sectionthrough an are substantially greater than degrees and terminates atopposite sides thereof in a pair of axially spaced oppositely disposedannular side wall parts which in transverse section are curved reverselythroughout with respect to the curvature of said main central wall partto define therebetween a relatively narrow opening extendingcireumferentially about the annular base of said main central wall part,all said parts of each bellows element being symmetrically disposed inrelation to the median plane of the element extending norial to the axisthereof, the main central wall part of each bellows element beingconcave to said internal pressure while the reversely curved side wallparts thereof are convex to said pressure, the reversely curved sidewall 1 parts providing respectively on opposite sides of the centralwall part of the bellows element a pair of oppositely presenting annularindentations equally spaced radially from the central longitudinal axisof the bellows element, the said indentations being each of a sameradius substantially less than that of the central wall part, saidreversely curved side wall parts being respectively provided withaxially alined tubular extremities of equal diameter at opposite sidesof said main central wall part, and a plurality of tubular sleevesdisposed alternately with respect to said bellows elements in coaxialalinement therewith, each adjoining pair of said bellows elements havingone of said sleeves extending therebetween to commonly embrace theproximate tubular extremities of each said adjoining pair of bellowselements, the ends of said sleeves in immediate proximity to saidbellows elements having edges which are shaped complementally to thetransverse curvature of said indentations and are snugly accommodatedtherein, said sleeves being adapted to support the reversely curved sidewall parts of the bellows elements against deformation under theinfluence of said internal pressure and to permit freedom of movement ofthe main central wall parts of the bellows elements when the latter arealternately expanded and contracted, and means for securely retaining ineach of said indentations the complementally shaped end of the sleevesnugly accommodated therein, said seen-ring means being in each instancespaced axially from said reversely curved side wall parts, each of saidbellows elements being further characterized in that the transverselycurved main central wall part and the reversely curved side Wall partsthereof are formed of continuously homogeneous metal entirely free ofany circumferentially extending welds.

5. in an expansion joint as defined in claim 4 wherein the aforesaidproximate tubular extremities of each adjoining pair of said bellowselements are in the form of a cylindrical part which extendscontinuously between and is commonly integral with said adjoining pairof said bellows elements.

References Cited in the file of this patent UNITED STATES PATENTS327,215 Youngs Sept. 29, 1885 1,239,978 Star Sept. 11, 1917 2,208,539Brown July 16, 1940 2,298,150 Newton Oct. 16, 1942 2,418,800 Wilson Apr.8, 1947 2,445,484 Kopperman July 20, 1948 2,489,844 Zallea Nov. 29, 1949FOREIGN PATENTS 191,911 Switzerland Dec. 1, 1937 498,403 Great BritainJan. 9, 1939

